1. Field of the Invention
This invention relates to the field of fittings for plastic pipes such as used in lawn irrigation systems and more particularly to the field of clampless fittings for such pipes.
2. Discussion of the Background.
Fittings for plastic pipes such as used in lawn irrigation systems are commonly secured to the pipes in any number of manners. However, the fittings are generally either positioned outside the open end of the pipe or received within the open end of the pipe.
Fittings that are designed to be positioned outside or over the pipe (i.e., the open end of the pipe is receive in the fitting) have several disadvantages. First, the outer diameter of such plastic pipes varies widely in the industry from manufacturer to manufacture even though the inner diameter may be standard and the same. Such fittings must then be able to accommodate pipes of different, outer diameters and different wall thicknesses. In many cases, such fittings must be specifically designed and may only fit or fit well with certain pipes made by certain manufacturers. The initial installer or repairer may then need to carry or have available a number of different fittings depending upon the pipes at the site. A second disadvantage of such fittings designed to be positioned over or outside the pipe is that the exterior of the pipe adjacent its open end invariably must be manually cleaned and cleared of all dirt and debris before insertion into the fitting otherwise the seal may leak. This may be difficult to do depending upon the conditions at the site (e.g., weather, cramped quarters of the hole, or time limitations) and may even be intentionally or unintentionally skipped by the installer. Further, due to these and other disadvantages, many exterior fittings often have fairly complicated and involved designs both to use and to manufacture and in many cases may require a number of parts including some that may need to extend into the pipe interior.
As mentioned above and unlike the outer diameter of such plastic pipes, the inner diameter for any particular gauge is essentially standard in the industry from manufacturer to manufacturer. Consequently, fittings designed to be received or inserted into the pipe versus over or outside the pipe can be designed to work with any pipe of a certain gauge regardless of the manufacturer. The cleaning step is also often not necessary as the exterior of the fitting and the inside of the pipe are usually relatively free of dirt and debris.
However, one common disadvantage of such fittings designed to be received in the open end of the pipe with the pipe then extending about the fitting is the need to use exterior clamps with them to securely hold and seal the pipe onto the fitting. This in turn requires the initial installer or repairer to carry and attach clamps at each connection. In the field, this can become burdensome and time consuming and the clamps may become lost or forgotten or an insufficient number of them may have been brought to the site. Clampless fittings or ones that can seal and hold themselves in the pipe without the need of an exterior clamp are most desirable but presently available ones often do not reliably operate in the field under all conditions.
With this and other problems in mind, the present invention was developed. In it, a clampless fitting is provided which can be inserted into the open end of a plastic pipe and will grip and reliably secure itself in place as the pipe and fitting are initially moved apart either manually or under the pressure of the water in the pipe. Additionally, the fitting will continue to remain in place and seal under normal operating conditions as the water in the pipe is cycled on and off alternately loading and unloading the pipe.